Topic: Global Ecology — the ecology of biosphere

Lecture 5

Section objectives:

1 Vernadsky V.I. - the founder of study of biosphere

2 Concept of biosphere living-component and its biogeochemical functions.

3 Biogeochemical Cycles: Water cycle. Nitrogen cycle. Oxygen-Carbon cycle.

4 Terrestrial and Aquatic biomes.

1. Vernadsky V.I. - the founder of study of biosphere.

The term "biosphere" was coined by geologist Eduard Suess in 1875, which he defined as: The place on earth's surface where life dwells.

Some life scientists and earth scientists use biosphere in a more limited sense. For example, geochemists define the biosphere as being the total sum of living organisms (the "biomass" or "biota" as referred to by biologists and ecologists). In this sense, the biosphere is but one of four separate components of the geochemical model, the other three being lithosphere, hydrosphere, and atmosphere. The narrow meaning used by geochemists is one of the consequences of specialization in modern science. Some might prefer the word ecosphere, coined in the 1960s, as all encompassing of both biological and physical components of the planet.

The founder of the study about biosphere - is V.I. Vernadsky (1868-1945). Biosphere - is that area of the earth where life exists. Scientific work “Biosphere” (1926). The main idea of his study is a concept of ‘living matter”.

2. Biosphere components:

• Aerobiosphere (Atmosphere) - air

• Hydrobiosphere (Hydrosphere) - water

• Lithobiospere (Lithosphere) - earth's crust

• Noosphere - biosphere transformed by people activity and changed by
scientific consciousness. The term “noosphere” was proposed by Le Rois (1927). From Greek: “noos” = “consciousness”.

A study of biosphere: study about the primary role of living organisms (living component) and their activity on the formation of earth's surrounding (Atmosphere, Hydrosphere Lithosphere).

Characteristics of biosphere:

1. The whole earth system
2. Self-regulation
3. Stability
4. Reproduction

Water when compare with air is the main limiting factor for life distribution. Life optimum is on the surface of surroundings division

The analysis of the average values for large squares shows that the productivity is between 200 and 20000 kcal/m² per year, and the total Earth productivity is about 10¹⁸ kcal per year.

Some theorists have postulated that the Earth is poorly suited to life, although nearly every part of the planet, from the polar ice caps to the Equator, supports life of some kind. Indeed, recent advances in microbiology have demonstrated that microbes live deep beneath the Earth's terrestrial surface, and that the total mass of microbial life in so-called "uninhabitable zones" may, in biomass, exceed all animal and plant life on the surface. The actual thickness of the biosphere on earth is hard to measure. Birds typically fly at altitudes of 650 to 2000 meters, and fish that live deep underwater can be found down to -8,372 meters in the Puerto Rico Trench.

For the last 100 years humankind has increased in numbers in 4 times, energy consumption – in 10 times, total product – in 17,6 times, mineral resources – in 29 times. 85% of all mineral resources that humans used throughout their history was extracted during XXth century. The total amount of used energy at the end of a century is only 3-4 orders of magnitude lower than solar energy entering the upper atmosphere. At present, ¼ of all land is occupied with agrocenosis and pastures and ¾ of the land not covered by ice turns out to be directly utilized. The world catch of fish has reached its theoretical limits. Changes in global climate of the Earth, intensifying the natural disasters, increasing damages and leading to extinction of many species, are clearly visible. The humans will double in size in XXIth century. Will biosphere withstand such load?

For the last 100 years humans in general have improved their life conditions. Scientific and technological advances have improved the work performance in many times and facilitated the lives of many millions of people. Mechanization, electrification, advances in chemical science and information breakthroughs became part of life of every human being in rich countries.

The World Community has started to help countries, that suffered from natural disasters – droughts, floods, earthquakes, fires. But even at ordinary periods, the World Community has provided significant food and medical help to poor countries. Such help decreased infant mortality and increased life expectancy in developing countries. Potent medications, aimed against inflammatory diseases (sulfamid medications, antibiotics) and a new vaccines aimed against infectious diseases were developed in the first half of this century. The natural spreading places of plague, malaria and other diseases, transferred by animals, were eliminated in many areas.

2. Concept of biosphere life-component and its biogeochemical functions.

Life-component - all living organisms presented as mass, energy and chemicals.

Biogeochemical functions of living component:

• Formation of gas composition of the Earth atmosphere: only due to the living component the free oxygen released into the atmosphere and the amount of carbon dioxide restricted.

• Concentration: organisms can accumulate some chemical elements in their bodies (sedimentary rocks, carbonates deposits)

• Redox reactions: oxidation of organic compounds to CO₂ and H₂O and their reduction to organic compounds.

• Biogeochemical activity of humans: people affect biosphere in different ways (anthropogenic factor, mostly industrial).

The food supply still depends on productivity of ecosystems. In theory, the total annual production of biosphere (dry weight) is about 141010 tons, and the production of all fields and pastures is about 2,8×10¹⁰ tons. All humans at present consume directly and indirectly about 2×10⁹ tons of grain per year (wet weight).

At present, all agricultural areas of humankind occupy 37% of all land, with fields and pastures occupying 28%. This area covers 4,1×10⁹ hectares. The proportion of woods is nor more than 31% of all land and the remaining land (about 32%) is mainly of low productivity.

Bearing this in mind, the warnings of the ecologists regarding continuing demolition of woods become clear. However, human population should double in size in the next 50 years. Would it be possible to supply everyone with food? This question is not trivial, if one considers that at present at least 1 billion of people are constantly underfed. It can be expected, that more and more poor countries will have the opportunity to modernize their agriculture and approach the productivity of land areas found in developed countries. However, these optimistic expectations will not solve the problem of food supply for population of more than 10 billions. Thus, the gap in food content of rich and poor countries will also be retained in the future. The food is obtained in abundance in rich countries, which partially export it to other regions, donate its small part as a humanitarian aid and sometimes, just destroy the food excess, as happening in Europe due to cattle epidemics. Poor countries are able to feed their people mainly with vegetative food – rice, maize, potato.

3. Biogeochemical Cycles: Water cycle. Nitrogen cycle. Oxygen-Carbon cycle.

Biogeochemical cycle - the process by which inorganic materials move from the atmosphere or soil into living organisms and back again.

Water Cycle: Of the nearly 1.5 billion km³ of water on the earth, less than 1% is available to land organisms.

Nitrogen Cycle: Includes 4 major processes: Nitrogen fixation - Ammonification - Nitrification - Denitrification

Carbon Cycle: Two main processes: Photosynthesis and Cellular Respiration

4. Terrestrial and Aquatic Biomes.

Terrestrial, or Land biomes:

Biome - is a large area identified by presence of characteristic (dominant) plants and animals, broadly defined life zones, environments with similar climates, topographies, soil conditions, and biological communities. Distribution mainly dependent on temperature and precipitation.

- Polar - biomes found at the earth's coldest extremes.

- Tundra - a treeless biome blanketed by snow in the winter.

Permafrost - a permanently frozen layer of ground over 500 m thick.

- Coniferous Forest - is a biome that is dominated by conifers, cone-bearing evergreen trees such as pines, firs, spruces, and cedars (Taiga).

- Deciduous forest - is a biome characterised by the presence of trees that lose their leaves in the fall.

- Grassland - is a biome dominated by grasses. Grasslands are known by various names in different regions of the world:

Prairie in North America

Steppes in Asia Pampas in South America

Veldt in South Africa

Savannas - is grassland with scattered trees found in tropical and subtropical areas.

- Desert - is an area where rainfall averages less than 25 cm per year. Water -is the limiting factor.

- Rain forests

Tropical rain forest biome - is found near the equator where rainfall and sunlight abound.

Temperate rain forest extends along the west coast of North America.

The major factors determining the characteristics of biomes include temperature and precipitation. Life is affected either by a lack or an abundance of either. For instance, where there is very little moisture, there will be deserts, whether they are in warm or extremely cold areas (like the north slopes of Alaska). Where there are extremely low or very high temperatures, life is also affected. Some of the most productive and diverse ecosystems are the wettest and warmest, including the tropical rain forests.

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